Transfer switch for tap changing regulating transformers including a contact support for the fixed contacts having no creepage path



A ril 18, 1967 BAUMGARTNER E. 3,315,043 TRANSFER SWITCH FOR TAP CHANGING REGULATING TRANSFORMERS INCLUDING A CONTACT SUPPORT FOR THE FIXED CONTACTS HAVING NO CREEPAGE PATH Filed June 8, 1966 3 Sheets-Sheet 1 I Mm W/ M NW Nmm 3,315,043; FORMERS p 19-67 E. BAUMGARTNER TRANSFER SWITCH FOR TAP CHANGING REGULATING TRANS I INCLUDING A CONTACT SUPPORT FOR THE FIXED CONTACTS HAVING NO GREEPAGE PATH 3 Sheets-Sheet 2 Filed June 8, 1966 p i 1967 E. BAUMGARTNER 3,315,043

TRANSFER SWITCH FOR TAP CHANGING REGULATING TRANSFORMERS INCLUDING A CONTACT SUPPORT FOR THE FIXED CONTACTS HAVING NO CREEPAGE PATH 3 Sheets-Sheet Filed June 8, 1966 United States Patent Claims. 61. 200-11) This invention relates to tap-changing regulating transformers, and more particularly to transfer switches for such transformers of the type known as Jansen-type transfer switches. An important feature of Jansen-type transfer switches resides in the fact that the movable contacts, or contact bridges, thereof are under the control of a snap-action operating mechanism imparting to'their contacts, or contact bridges, high switching velocities.

It is a general object of this invention to provide improved transfer switches of the above description.

Another object of this invention is to provide improved transfer switches for tapped regulating transformers particularly suited for high voltage applications wherein dangerous creepage paths are entirely eliminated.

Another object of this invention is to provide improved transfer switches for tapped regulating transformers the constituent parts of which are readily exposed to view to facilitate inspection, maintenance and repair of the transfer switches.

Another object of this invention is to provide improved transfer switches for regulating transformers having fixed contacts that are more readily accessible for inspection, maintenance, repair and replacement than the fixed contacts in comparable prior art transfer switches.

In polyphase designs of transfer switches the movable contacts and the fixed contacts and the contact operating means pertaining to all phases are integrated into a structural unit. Single-phase transfer switches include only the parts required for one single phase;

I Itis a special object of this invention to provide improved transfer switches for single-phase switching duty.

Still another object of this invention is to provide an improved version of the transfer switches disclosed and claimed in US. Patent 3,250,865 to Alexander Bleibtreu, issued May 10, 1966 for Transfer Switch for Tapped Regulating Transformers with Radial Guide and Linkage Structure, assigned to the same assignee as the present invention.

A further object of this invention is to provide improved single-phase transfer switches for tapped regulating transformers including a frame structure having a high degree of dimensional stability.

For a better understanding of the present invention,

together with other objects and advantages thereof, reference may be had to the following description taken in connection with the accompanying drawings, and its scope will be pointed out in the appended claims.

Referring now to the drawings:

FIG. 1 is a diagrammatic representation of the circuit, the contacts and the contact-operating mechanism of a transfer switch embodying the present invention;

FIG. 2 is substantially a vertical section of a transfer switch embodying the present invention taken along IIII of FIG. 3;

3,315,043 Patented Apr. 18,1967

FIG. 3 is substantially a horizontal section of the structure illustrated in FIG. 2 taken along III-III of FIG. 2;

FIG. 4 is in part a front elevation and in part a sec tion taken along IV-IV of FIG. 3 and shOWS on a larger scale a detail of the structure of FIGS. 2 and 3; and

FIG. 5 is a section along VV of FIG. 4.

Referring now to the drawings, and more particularly to FIG. 1 thereof, reference character Tr has been applied to indicate a transformer winding having two taps U and U and reference characters R and R have been applied to indicate a pair of ohmic tap-changing resistors, or switch-over resistors, of a transfer switch. The transfer switch further comprises four movable contact bridge-s 27, 28, 29, 30. Movable contact bridge 27 is adapted to engage a pair of fixed contacts 23, 23 and to part from fixed contacts 23, 23. Movable contact bridge 28 cooperates in the same fashion with fixed contacts 24, 24'. The same applies in regard to movable contact bridge 29 and fixed contacts25, 25', and in regard to movable contact bridge 30 and fixed contacts 26, 26'.

In the position of the transfer switch shown in FIG. 1 contact bridge 27 is in engagement with fixed contacts 23, 23 and contact bridge 29 is in engagement with fixed contacts 25, 25. Contact bridge 28 is out of engagement with fixed contacts 24, 24' and contact bridge 30 is out of engagement with fixed contacts 26, 26'. In the position of the transfer switch shown in FIG. 1 tap U of winding TI is conductively connected to the transfer switch terminal T by the following current path: tap U lead a, fixed contact 23, contact bridge 27, fixed contact 23', lead b, terminal T.

If terminal T is to be disconnected from tap U and to be connected to tap U the following switching operations must'be carried out sequentially in the specific sequence which is indicated below:

Contact bridge 27 must part from fixed contacts 23, 23, while contact bridge 29 remains in engagement with fixed contacts 25, 25' and contact bridges 28 and 30 remain in their off positions. This establishes the following current path: tap. U lead 0, resistor R lead a, fixed contact 25, contact bridge 29, fixed contact 25', lead b, terminal T.

The next step consists in engagement of contact bridge 30 and fixed contacts 26, 26', contact bridges 27 and 28 remaining in the open position thereof. As a result the following current path is added to the aforementioned current path: tap U lead e, resistor R lead f, fixed contact 26, contact bridge 30, fixed contact 26, lead g,

shunt path for circulating currents including resistors R and R is interrupted.

The last step in the tap-changing switching operation of the transfer switch shown in FIG. 1 is closing of contact bridge 28, contact bridge 30 remaining in the closed position thereof and contact bridges 27 and 29 remaining in the open positions thereof. The last referred-to switching step establishes the following direct current path between tap U and terminal T: tap U lead h, fixed contact 24, contact bridge 28, fixed contact 24, lead g, terminal T.

It appears from the foregoing that changing from tap U to tap U involves the following sequential steps:

(1) Contact bridge 27 opens. (2) Contact bridge 30 closes. (3) Contact bridge 29 opens. (4) Contact bridge 28 closes.

A certain time elapses between consecutive switching steps, and the timing of such steps is referred to as the speed at which the tap-changing operation is performed.

As shown in FIG. 1 each contact bridge 27, 28, 29, 30 is operated by a link 31 pivotally connected to the respective contact bridge 27, 28, 29, 30. The ends of links 31 remote from contact bridges 27, 28, 29, 30 are pivotally supported on a vertical floating shaft 33. Shaft 33 is under the action of a helical tension spring 36 whose radially outer end is attached to a pivot 38. Pivot 38 is arranged at the radially outer end of lever 40 fulcrummed at 42. Lever 40 is operable by a shaft and a lever 48 integral with shaft 15. Shaft 15 is arranged eccentrically inside the circle defined by fixed contacts 23, 23'; 24, 24'; 25, 25; 26, 26. The radially outer end of lever 48 is pivotally connected to lever 40 and that pivot is slidable in a direction longitudinally of lever 40 by means of an oblong hole or slot provided in lever 40. This mechanism is designed to sequentially operate the four movable contact bridges 27, 28, 29, 30 in the manner set forth above.

Shaft 15 may be pivoted selectively in clockwise and counterclockwise direction by appropriate motor means (not shown) such as, for instance, a spring motor. Spring 36 is an over-center spring. When shaft 15 is pivoted in clockwise direction its motion is transmitted by lever 48 to lever 40, thus causing the latter to pivot in clockwise direction, as seen in FIG. 1, about its fulcrum 42. The radially outer end 38 of lever 40 moves initially from its position along the center line between fixed contacts 23', 25, i.e. the line bisecting the angle 23, 42, 25, to its position along the center line between fixed contacts 25, 26. This causes sequential parting of contact bridge 27 from fixed contacts 23, 23 and engagement of fixed contacts 26, 26 by contact bridge 30. Over-center spring 36 becomes operative to perform the aforementioned switching operation when the path of movement of the radially outer end 38 of spring 36 intersects the line connecting the center of floating shaft 33 with a point at which contact bridge 29 is pivotally connected to its operating link 31.

As the clockwise pivotal motion of shaft 15 continues, the radially outer end of spring 36 is moved from a position midway between contacts 25', 26 to a position in which it bisects the angle enclosed between fixed contacts 24, 26' and fulcrum 42. As a result, movable contact bridge 29 separates from fixed contacts 25, 25 and movable contact bridge 28 engages fixed contacts 24, 24, contact bridge 27 remaining separated from fixed contacts 23, 23 and contact bridge 30 remaining in engagement with fixed contacts 26, 26'. Thus the change-over from tap U to tap U of FIG. 1 is completed.

The foregoing switching steps are reversed when shaft 15 is pivoted counterclockwise, resulting in a movement of the constituent parts of the transfer switch to their positions shown in FIG. 1.

Normally a tap-selector switch is interposed between a tapped transformer winding and a transfer switch. Provision of such a tap-selector switch is necessary any time the number of taps of a tapped transformer winding exceeds two. In FIG. 1 the number of taps has been limited to two and a tap-selector switch has been omitted in order not to add matter which is not essential for an understanding of the present invention which is limited to the transfer switch proper.

In FIGS. 2 and 3 the same reference characters have been applied as in FIG. 1 to designate like parts. The structure of FIGS. 2 and 3 differs from that of FIG. 1 in that the fixed contacts 23, 23', 24, 24' are arranged along vertical lines in superimposed registering pairs rather than in a horizontal plane as shown in FIG. 1, and in that each of the contact bridges 27, 28, 29, 30 defines a vertical plane rather than being arranged in a common horizontal plane, as shown in FIG. 1.

Referring now to FIGS. 2-5 numeral 60 has been applied to indicate a switch support formed by hollow cylinder of insulating material. Cylinder 60 is provided with a flange and a plurality of rods 62 project transversely through flange 61. The upper ends and the lower ends of rods 62 are screw-threaded and the upper ends of rods 62 are provided with shoulders screwed by means of nuts against the lower surface of flange 61. Rods 62 support the upper horizontal end plate 44, the lower horizontal end plate 45 and the intermediate horizontal partition 53. Reference character 63 has been applied to indicate tubular spacers mounted on rods 62 to maintain end plates 44, 45 and partition 53 in the respective position thereof. The aforementioned parts form a rugged frame structure which is substantially in the shape of a squirrel cage.

Reference numerals 27, 28, 29, 30 have been applied to indicate four movable contact bridges of which each is pivotally connected to a pair of bridgeoperating levers 31, 32. The ends of levers 31, 32 remote from contact bridges 27, 28, 29, 30 are pivotally supported by a vertical floating shaft 33. One end of helical spring 36 is pivotally connected to floating shaft 33 as indicated at 34. In a like fashion, one end of helical spring 37 is pivotally connected to floating shaft 33, as indicated at 35. The ends of helical springs 36, 37 remote from floating shaft 33 are pivotally connected to levers 40 and 41, as indicated at 38 and 39, respectively. The ends of levers 40, 41 remote from pivots 38 and 39 rest in bearings 42 and 43, respectively, and thus levers 40, 41 are pivotable inside of horizontal parallel planes. Bearing 42 is integral with the aforementioned horizontal upper end plate 44 and bearing 43 is integral with the aforementioned horizontal lower end plate 45. Levers 40, 41 are each provided with a slot, or oblong hole, 46 and 47, respectively. Levers 48 and 49 are both fixedly mounted on driving shaft 15, and the ends thereof remote from driving shaft 15 are provided with projections, e.g. rollers, engaging the aforementioned slots, or oblong holes, 46, 47 in levers 40, 41. The upper end of driving shaft 15 supports a tube 14 of insulating material for insulating the motor means (not shown) of driving shaft 15 from the latter. Partition 53 is provided with angularly displaced radial slots 51 forming straight guiding means for movable contact bridges 27, 28, 29, 30.

In accordance with the principle underlying this invention the upper end plate 44 and the lower end plate 45 are provided with radial slots 64. Slots 64 are wider at some point between the ends thereof than at the ends thereof, i.e. at the closed end thereof and at the open end thereof. Thus a pair of cantilever-like projections 65, 66 is formed to the sides of slots 64. A vertical insulating plate 67 is arranged between each pair of projections 65, 66 formed by upper end plate 44. In a like fashion, a vertical insulating plate 68 is arranged between each pair of projections 65, 66 formed by lower end plate 45. The height of plates 67, 68 is relatively small and substantially less than the spacing between end plates 44, 45. Upper insulating plates 67 support the stationary contacts 23, 24, 25, 26, and lower insulating plates 68 support the stationary contacts 23, 24', 25, 26'. Pairs 23- and 23; 24 and 24'; 25 and 25'; 26 and 26' of contacts are arranged in registry. Each fixed contact is arranged in a separate switching chamber defined by a substantially box-shaped element 69 housing the respective contact and screwed against the aforementioned vertical insulating plates 67, 68. This way of housing the fixed contacts is clearly shown in FIGS. 4 and 5 which refer to fixed contact 23. All the other fixed contacts are housed in the same fashion as fixed contact 23. l

The edges of projections 65, 66 of end plates 44, 45 support a molding formed of two separate complementary parts 70 and 71. As shown in the drawings part 70 is screwed against projections 65, 66 by means of screws 74, and part 71 is screwed against part 70 by means of screws 75. Parts 70 and 71 jointly define vertical grooves 72 for receiving the aforementioned contact supporting insulating plates 67 and 68, respectively. Insulating caps 73 have a substantially U-shaped portion fitting into grooves 72. These caps are inserted into grooves 72 and interposed between groove-defining moldings 70, 7] on the one hand, and contact-supporting plates 67, 68, on the other hand.

It is apparent from the drawings that the upper contacts 23, 24, 25, 26 are widely spaced from the lower contacts 23, 24', 25, 26, and that the upper contacts and the lower contacts are insulated by a body of oil when the transfer switch is immersed in oil, there being no creepage paths between the upper contacts and the lower contacts. It will also be apparent that the entire fixed contact units including switching-chamber-defining elements 69 and contact-supporting insulating plates 67 and 68, respectively, may readily be removed from the transfer switch by loosening of screws 74. Upon removal of the aforementioned fixed contact units each of them may readily be disassembled by loosening screws 75, thus making it readily possible to repair or replace an eroded contact. Even without disassembling any portion of the transfer switch structure, all its constituent parts are exposed to visual inspection, thus making it possible to simplify its maintenance and to readily diagnose any cause of malfunctioning.

It will be apparent from the foregoing that the contactoperating mechanism of the structure of FIGS. 2-5 Works in exactly the same fashion as that described in detail in connection with FIG. 1.

While the transfer switch which has been illustrated and described is a single-phase transfer switch, such switches are not limited to single-phase applications. Several such switches may be combined for polyphase applications, e.g., in connection with delta-connected transformers.

Single-phase transfer switches are often used in applications involving large blocks of power and requiring large contact-operating forces. The squirrelcage-like frame structure 44, 45, 62, 63 imparts to the transfer switch the dimensional stability so essential in applications involving large blocks of power and large contactoperating forces.

While there has been described what is at present considered to be the preferred embodiment of the invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the invention, and it is, therefore, aimed to cover all such changes and modifications as fall Within the true spirit and scope of the invention.

I claim as my invention:

1. A transfer switch for tapped regulating transformers comprising in combination:

(a) a first plurality of fixed contacts arranged around a center in a circular pattern;

(b) a second plurality of fixed contacts arranged around said center in a circular pattern, each of said second plurality of contacts being arranged in registry with one of said first plurality of contacts;

(c) a plurality of movable contact bridges each cooperating with one of said first plurality of fixed contacts and one of said second plurality of fixed contacts;

(d) a plurality of link means each operatively related to one of said plurality of contact bridges for moving said one of said plurality of contact bridges into and out of engagement with one of said first plurality of fixed contacts and one of said second plurality of fixed contacts;

(e) contact operating means pivotally connected to the ends of said plurality of link means remote from said first plurality of fixed contacts and said second plurality of fixed contacts for operating said plurality of contact bridges in a predetermined sequence;

(f) common shaft means for operating said contact operating means;

(g) a pair of parallel spaced plates having bearing means for supporting said shaft means, each of said pair of plates having a plurality of slots extending radially inwardly from the periphery thereof;

(h) a plurality of spacing rods extending parallel to said shaft means and integrating said pair of plates into a squirrel-cage-like frame structure;

(i) a first plurality of contact-supporting insulating members each inserted into one of said plurality of slots in the upper of said pair of plates and each supporting one of said first plurality of fixed contacts; and

(j) a second plurality of contact-supporting insulating members each inserted into one of said plurality of slots in the lower of said pair of plates and each supporting one of said second plurality of fixed contacts.

2. A transfer switch as specified in claim 1 wherein (a) said contact operating means include a floating shaft pivotally supporting the ends of said link means remote from said first plurality of fixed contacts and remote from said second plurality of fixed contacts, said floating shaft being under the action of over-center spring means having one end pivotally secured to said floating shaft and the other end operatively related to said common shaft means; and wherein (b) each of said first plurality of insulating members and each of said second plurality of insulating members is formed by a contact-supporting plate arranged substantially at right angles to the planes defined by said pair of parallel spaced plates and having a predetermined height substantially less than the spacing between said pair of parallel spaced plates.

3. A transfer switch as specified in claim 1 wherein the width of each of said plurality of slots in said pair of parallel plates is less adjacent the open end thereof and the closed end thereof than at a point intermediate said open end and said closed end whereby a pair of cantiliver-like projections is formed adjacent each of said plurality of slots in said pair of parallel plates.

4. A transfer switch as specified in claim 1 wherein each of said parallel pair of plates is shaped to form a pair of cantilever-like projections adjacent each of said plurality of slots therein, said switch further including a plurality of pairs of molds each pair being secured to one of said pair of projections and defining a pair of parallel grooves, each said pair of parallel grooves adjacent one of said pair of parallel plates receiving one of said first plurality of contact-supporting insulating members, and each said pair of parallel grooves adjacent the other of said pair of parallel plates receiving one of said second plurality of contact-supporting insulating members.

5. A transfer switch as specified in claim 1 wherein each of said parallel pair of plates is shaped to form a pair of cantilever-like projections adjacent each of said plurality of slots therein, said switch further including a plurality of pairs of molds each pair being secured to one of said pair of projections and defining a pair of parallel grooves, a plurality of pairs of insulating caps each pair having substantially U-shaped projections and deli Hing substantially U-shaped grooves, each pair of caps being fitted With said projections thereof into one of said pair of parallel grooves defined by one of said pair of molds, said grooves in each pair of said plurality of pairs of caps adjacent one of said pair of parallel plates being engaged by one of said first plurality of contact-supporting insulating members, and said grooves in each pair of said plurality of pairs of caps adjacent the other of said pair of parallel plates being engaged by one of said second plurality of contact-supporting insulating members.

References Cited by the Examiner UNITED STATES PATENTS 3,238,318 3/1966 Bleibtreu et al 2U0-11 3,250,865 5/1966 Bleibtreu 20011 3,258,546 6/1966 Blei btreu 200-11 X ROBERT K. SCI-IAEFER, Primary Examiner.

I. R. SCOTT, Assistant Examiner. 

1. A TRANSFER SWITCH FOR TAPPED REGULATING TRANSFORMERS COMPRISING IN COMBINATION: (A) A FIRST PLURALITY OF FIXED CONTACTS ARRANGED AROUND A CENTER IN A CIRCULAR PATTERN; (B) A SECOND PLURALITY OF FIXED CONTACTS ARRANGED AROUND SAID CENTER IN A CIRCULAR PATTERN, EACH OF SAID SECOND PLURALITY OF CONTACTS BEING ARRANGED IN REGISTRY WITH ONE OF SAID FIRST PLURALITY OF CONTACTS; (C) A PLURALITY OF MOVABLE CONTACT BRIDGES EACH COOPERATING WITH ONE OF SAID FIRST PLURALITY OF FIXED CONTACTS AND ONE OF SAID SECOND PLURALITY OF FIXED CONTACTS; (D) A PLURALITY OF LINK MEANS EACH OPERATIVELY RELATED TO ONE OF SAID PLURALITY OF CONTACT BRIDGES FOR MOVING SAID ONE OF SAID PLURALITY OF CONTACT BRIDGES INTO AND OUT OF ENGAGEMENT WITH ONE OF SAID FIRST PLURALITY OF FIXED CONTACTS AND ONE OF SAID SECOND PLURALITY OF FIXED CONTACTS; (E) CONTACT OPERATING MEANS PIVOTALLY CONNECTED TO THE ENDS OF SAID PLURALITY OF LINK MEANS REMOTE FROM SAID FIRST PLURALITY OF FIXED CONTACTS AND SAID SECOND PLURALITY OF FIXED CONTACTS FOR OPERATING SAID PLURALITY OF CONTACT BRIDGES IN A PREDETERMINED SEQUENCE; (F) COMMON SHAFT MEANS FOR OPERATING SAID CONTACT OPERATING MEANS; (G) A PAIR OF PARALLEL SPACED PLATES HAVING BEARING MEANS FOR SUPPORTING SAID SHAFT MEANS, EACH OF SAID PAIR OF PLATES HAVING A PLURALITY OF SLOTS EXTENDING RADIALLY INWARDLY FROM THE PERIPHERY THEREOF; 